(a) Field of the Invention
The present invention relates to an inflatable fabric that can be inflated with air, and more particularly to an inflatable fabric that can be used for car airbags, life jackets, and so forth.
(b) Description of the Related Art
An inflatable fabric can be used for car airbags, life jackets, and the like. The inflatable fabric is especially useful for a side curtain type of airbag which is unfolded at the side windowpane to protect an occupant's head from being hurt by collision with the windowpane or other structures when a car overturns in an accident. For the airbag to safely protect the occupant, it should be at an inflated state for at least 5 seconds when the car rolls over, and the inflatable fabric is useful for this purpose.
In general, methods for manufacturing inflatable fabrics for car airbags are classified into: 1) a method of sewing, sewing, fusing, or adhering two fabrics; and 2) a method of using a two-layer fabric wherein the two layers of the fabric are partly joined by an attachment area.
However, the first method for preparing the inflatable fabric by sewing, fusing with heat or microwave treatment, or adhering the two fabrics with adhesive requires additional sewing, fusing, or adhering procedures following manufacturing of the two fabrics after preparation of the textile fabric consisting of the two layers, resulting in complicated procedures and increasing manufacturing costs.
To solve this problem, the second method for preparing the inflatable products such as the airbag with the two inflatable layers has been furthered recently.
An inflatable fabric that is inflated by air or another gas has two separate fabric layers and an attachment area between the layers. The fabric enclosed by such an attachment area strongly interlocks the two layers when each individual layer rapidly inflates, so that air or a gas does not leak out.
Methods for forming an attachment area in the inflatable fabric have been proposed by U.S. Pat. Nos. 6,220,309, 5,098,125, 5,011,183, 5,603,647 and 6,595,244.
U.S. Pat. No. 6,220,309 discloses a fabric whose separator area is formed in a plain weave and whose attachment area is formed in a 2/2 basket weave. U.S. Pat. No. 5,098,125 and U.S. Pat. No. 5,011,183 disclose a two-layer fabric whose separator area is formed in a plain weave and whose attachment area is formed in (a 2/2 basket or 3/3 basket weave)+(a 1/2 twill or 1/3 twill wave)+(a 5 harness satin). U.S. Pat. No. 5,603,647 discloses a two-layer fabric whose separator area is formed in a plain weave, a basket weave or a twill weave and whose attachment area is formed in a 3/3 basket weave. Here, the separator area refers to the area in the fabric where the two fabric layers (upper and lower layers) are separated from each other, so that the fabric may inflate by air, etc. In addition, the attachment area refers to the area where the two separated fabric layers are attached to each other.
The above-mentioned two-layer fabrics mainly utilize attachment areas formed in a 3/3 basket weave or a 2/2 basket weave. However, if they are used alone, air or gas may leak out at the attachment area, resulting in a high breathability property when the two separated layers inflate.
U.S. Pat. No. 6,595,244 discloses a fabric whose attachment point comprises at most a 12 yarn basket weave. However, the attachment point is not strong enough because the single fabric layer (basket weave) is formed solely from one type of yarn. If the middle of the two-layer fabric is changed into a basket pattern in order to increase strength, tension applied to the yarns at the attachment point becomes too high due to the whole attachment point consisting of the basket weave, so that weaving becomes very difficult and the shape and performance of the fabric may be negatively affected.